FhirXmlPocoDeserializer should throw an error when encountering multiple non-repeatable elements.

[mmsmits]

FhirXmlPocoDeserializer doesn't catch invalid repeating elements.

Here's a unit test that proves this:

        [TestMethod]
        public void TryDeserializeMultipleNonRepeatingValues()
        {
            var content = "<name xmlns=\"http://hl7.org/fhir\" >" +
                                "<family value=\"oof\"/>" +
                                "<family value=\"bar\"/>" +
                          "</name>";

            var reader = constructReader(content);
            reader.Read();
            var state = new FhirXmlPocoDeserializerState();

            var deserializer = getTestDeserializer(new());
            var datatype = deserializer.DeserializeElementInternal(typeof(TestHumanName), reader, state);

            datatype.Should().BeOfType<TestHumanName>();
            datatype.As<TestHumanName>().Family.Should().Be("bar"); 

            state.Errors.Should().HaveCount(1);
        }

Todo:

• Add a new error to FhirXmlException that describes the kind error
• Throw this new error when encountering multiple non-repeating elements.

[ewoutkramer]

This was fixed by #2434.